The objective of this study is to determine the role played by light-induced free radicals and active oxygen species (superoxide, singlet oxygen) in chemically induced skin photosensitization. Irradiation of the following chemical agents in aqueous or organic solvents has been shown to produce a variety of free radicals and/or oxygen derived species: benoxaprofen, benzoxazole, 2-methylbenzoxazole, 2-phenylbenzoxazole, musk ambrette, anthracene and fluoranthene. These photoinduced species may play an important role in the phototoxic and photoallergic properties of these agents.